you'll want to tune your print file using the test block so the the letters are snug but can slide in and the flowers and flag press fit well using x-y compensation. In bambu slicer theres separate setting for hole (flowers) and contour (letters) compensation. 

you'll also want to print the letters in occurrence to how often they occur in first names, heres what gemini suggested, but i think Z's are actually more common in kids names at the moment. You will need way more letters than you think since running out of one letter will kinda ruin the activity, especially vowels.

Relative Letter Frequency (suggested number per batch)

• A13

• E11

• I, N9

• L, R8

• O, S7

• T5

• D, M, Y4

• C, H, U3

• B, G, K, P2

• F, J, Q, V, W, X, Z1

AI was used to create the wreath geometry because who has time for blender, then manually edited to add the name slot and peg holes, everything else was done in tinkercad.